Jointed Birch Side Table

[Bill Packman]

I have received a large order for some Birch side tables however I am worried that without and bracing they will move considerably.

My shop is in Southern China (I am from UK but have been living over here for a few years now) and as such the humidity is very high. These tables will ship to Northern Europe - a more drastic environment change you'd be hard pressed to find.

The tables are fairly small (see attached) and normally I wouldn't worry too much but this is a decent size order and I will have no way to rectify my mistake should I make one.

In the picture there is a large central recess (I will be CNC cutting these pieces). This will accept a steel plate mounting point for the steel leg assembly. To either side is my idea.... If I were to cut 2 recesses (say 1/2" deep) across the grain of the jointed board, and glue in to them corresponding size pieces of birch would that stabilise the tables?

I know that good practice is to allow the wood to move to some extent. This solution is a little less sympathetic to the natural movement and seeks instead to bully the pieces into staying true but for a piece this small I am banking on the braces to be able to hold firm the jointed board.

Any advice gratefully received

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[Jamie Buxton]

Is the grain direction of the glued-in pieces running across the grain direction of the larger piece? If so, that isn't a great idea. The larger piece is likely to shrink cross-grain when it arrives in the dry climate. The cross pieces will not change in length. At the very least, you'll be stressing the wood. At the worst, something will break or crack. Furthermore, a little brace like that -- what it is, less than a cm square in cross section? -- will have little effect on the bigger board if it decides it wants to cup.

[Andrew Hughes]

I also think they will buckle and crack. There’s just really no stopping wood cells from gaining and losing water then changing their shape.
Do you have time ? Build one then put into a kiln bring down the mc and see for yourself.
It really fascinating how much a panel will shrink then crack a very well built frame.
Why don’t you make them from birch plywood it’s nice stuff.

[Warren Wilson]

Here is a wood shrinkage calculator: https://www.popularwoodworking.com/t...and-expansion/

Would it require much more time and material to use conventional buttons to attach top to legs?

[Wayne Lomman]

Your cross braces won't do any good and probably create new problems. Consider getting your timber dried to 8% and manufacturing without delay so that you can deliver a product closer to the destination requirements. Especially get coating done early and equally both sides so that moisture gain/loss is minimised and balanced. Impose strict procedures do that raw timber is never left with one side uncovered for very long. If you have a stack of tops, place them on a solid base and cover them with a solid piece of ply. Also consider mounting the steel plate 90 degrees to what you have drawn. This way you have a wider cross grain support. Make up your tops using narrow planks. This removes the wide plank cupping problem. Cheers

[Bill Packman]

Very sorry for the extremely long delay in replying. Your advice is very much appreciated and thanks for taking the time to post.

I ended up going back to the customer and suggesting birch plywood - and they agreed. Much more like it.